Screw separator

ABSTRACT

A screw separator for separating solids out of suspensions, having at least one housing and at least one feed pipe for the suspension, at least one discharge pipe for liquids, and at least one outlet for the at least partially dewatered solids. At least one strainer basket is provided in the housing in which a screw is rotatably mounted where at least one press basket is mounted downstream of the strainer basket, and the strainer basket is received in the housing radially floating and the press basket, radially fixed.

BACKGROUND

The present invention relates to a screw separator or a screw pressseparator for separating solids out of suspensions, comprising a housingand a suspension feed pipe, a liquids discharge, and an outlet for thedewatered solids.

These screw separators, often called filter screw presses, are per seknown from the prior art. Screw separators have also become known inwhich two series-connected, separate filter screens are provided whichare configured as strainer baskets. The first strainer basket serves asa liquid filter for separating out the bulk of the liquid portion whilethe downstream press basket comprises the solids compacted to form aslug. The pressure prevailing in the press basket is considerablyincreased such that maximum stresses occur there.

The known prior art is reliable in operation. There is the drawback,however, that the necessary precise matching of the press basket withthe strainer basket involves high manufacturing requirements makingthese screw separators complex and expensive. Moreover the strainerbasket and the press basket wear out rather quickly in operation.

It is therefore the object of the present invention to provide animproved screw separator which operates reliably and which is subjectedto reduced wear while the quality is maintained or even improved.

SUMMARY

The screw separator according to the invention serves for separatingsolids out of suspensions, comprising at least one housing having atleast one suspension feed pipe, at least one discharge for the separatedliquid, and at least one outlet for the at least partially dewateredsolids. The housing is provided with at least one strainer basket inwhich a screw is rotatably mounted. At least one press basket is mounteddownstream of the strainer basket. The strainer basket is received inthe housing radially floating and the press basket, radially fixed.

The screw separator of the invention has many advantages. A considerableadvantage of the screw separator according to the invention consists inthat the strainer basket is supported radially floating while the pressbasket is received radially fixed. In this way the strainer basket canadjust its position to the currently prevailing conditions while thepress basket maintains its fixed position. For example if a coarse solidparticle should be jammed at the edge of the screw vanes between thescrew vanes and the strainer basket, then the floating support of thestrainer basket allows the strainer basket to deflect radially whileavoiding transfer of the arising pressure to the housing. On the otherhand the slug guidance in the press basket is defined.

According to another configuration according to the invention the screwseparator serves for separating solids out of suspensions, comprising atleast one housing having at least one suspension feed pipe, at least onedischarge for the separated liquid, and an outlet for the at leastpartially dewatered solids. The housing is provided with at least onestrainer basket in which a screw is rotatably arranged. At least onepress basket is mounted downstream of the strainer basket. The housingcomprises at least one filter housing with the strainer basket mountedthereat or therein, and a press housing separate therefrom with thepress basket mounted thereat or therein.

This screw separator of the invention again has many advantages. It isquite a considerable advantage of a screw separator according to theinvention that the housing on the whole comprises at least one filterhousing and a press housing separate therefrom. In the filter housing astrainer basket is provided through which the bulk of the dewateringsubstance flows while the press basket is mounted at the press housing.The press basket substantially contains the slug formed duringoperation.

The two-part housing structure provides ease of opening for the housing.This allows easy replacement of the press basket mounted in the presshousing as needed. Moreover the strainer basket in the filter housing isreadily accessible so as to allow routine maintenance checks and thelike with minor effort.

In a particularly preferred configuration of the screw separatorsaccording to the invention the press housing is configured as a frontcover which can be swung away or pivoted or it comprises such a frontcover.

Preferably the front cover is mounted to the filter housing by means ofat least one hinge or similar flap mechanism to be pivotal in particularin two or three positions. Multiple pivoting options in particular aboutparallel pivot axes offer the considerable advantage to virtually allowaxial displacement due to the various pivot axes. This allows axialpulling of the front cover forwardly and subsequently pivoting it aroundone of the pivot axes so as to provide ready access to both the interiorof the press housing and the interior of the filter housing.

Preferably at least one in particular replaceable ring is providedbetween the strainer basket and the press basket. The ring is inparticular configured as a wearing ring and it may consist of plastic atleast in part and/or of metal at least in part.

Such a wearing ring allows cost-effective operation of a screw separatoraccording to the invention since the screw separator is preferablyconfigured and structured such that in particular the wearing ring isthe part most subjected to wear and in this way it can be replaced on aregular basis.

Preferably the wearing ring is configured to be tight in the radialdirection. Or else the wearing ring may be configured to be permeable toliquids at least in sections or partially.

It is particularly preferred for the press basket and the wearing ringto be mounted in the front cover, both being pivoted along as thehousing is opened. Advantageously the front cover is secured by way ofat least one quick release. This allows on the whole to quickly andeasily open up the housing for carrying out necessary maintenance orrepairs. In the prior art the housing is accessible from the end onlysuch that the components must be removed from the separator prior tochecking, maintenance, or replacement.

In all of the configurations the front cover is preferably provided withthe outlet or mouthpiece for the separated solids to emerge forwardlyout of the mouthpiece or the outlet of the screw separator.

Advantageously the outlet is provided with a flap cover mechanism whichis biased in the closed position. The flap cover mechanism may beconfigured as a spring flap cover mechanism comprising 2, 3, or 4 or yetmore flap sections which are distributed over the circumference andindividually or jointly biased in the closed position.

In particularly preferred configurations the screw is supported on thefeeder side and may be guided at its free end. Preferably a pipe or apipe-like structure is mounted in the press housing axially followingthe worm shaft of the screw and extending in particular as far as theoutlet and particularly preferably through the outlet to the exterior.Preferably the pipe or the pipe-like structure axially closely followsthe end of the worm shaft to reliably prevent the slug which may be ahollow cylinder from collapsing. Thus the slug will at all times beentirely supported from the interior over its entire length. Thepipe-like structure may be configured to be hollow inside or else solid.

Preferably at least part of the pipe is received rotatably. Or else itis conceivable for at least part of the pipe to be received stationary.In preferred configurations the entire pipe is received stationary. Orelse it is conceivable for the pipe to constitute a worm shaft extensionthat is mounted rotatable relative to the worm shaft.

The pipe-like structure or the pipe may be cylindrical in shape or itmay have or comprise a cone section shape.

In all of the configurations it is preferred for the screw to beprovided with at least two screw flights.

Advantageously the strainer basket is retained in the housing radiallyfloating. The strainer basket may be mounted radially floating inparticular in a range between 0.5 and 6 mm, preferably in a rangebetween 1 and 3 mm and particularly preferably by approximately 2 mm.

In contrast thereto the press basket is retained radially fixed and inparticular axially fixed as well.

The inner diameter of the press basket is preferably larger than theinner diameter of the strainer basket to ensure a smooth transition ofthe slug from the strainer basket into the press basket.

In particular the manufacturing tolerance of the press basket may beconsiderably larger than the manufacturing tolerance of the strainerbasket. Care is taken, however, for the maximally possible innerdiameter of the strainer basket including the possible manufacturingtolerance to not exceed the minimally possible inner diameter of thepress basket.

The inner diameter of the strainer basket is matched to the outerdiameter of the screw. The remaining radial gap between the radiallyouter sides of the filter screw and the inner surface of the strainerbasket is <2 mm and in particular <1 mm and particularly preferably inthe range between 0.2 and 0.7 mm. In specific configurations the gap isless than 0.5 mm.

The gap width is in particular less than 1% of the outer diameter of thescrew vanes, in particular less than 0.5% of the outer diameter of thescrew vanes and particularly preferably between 0.05% and 0.3% of theouter diameter of the screw vanes.

If the gap is too wide, water may spurt through the screw separator suchthat the function achieved is insufficient. On the other hand, too widegaps cause the sediment removal from the strainer basket to beinterrupted such that the strainer basket will clog up and the filteringfunction of the strainer basket is no longer ensured.

All of the configurations allow provision of at least one inspectionhole in the housing which is in particular fastened by at least onequick release. At least one inspection hole may be closed by atransparent inspection glass to allow looking into the housing from theexterior even when it is closed.

In all of the configurations preferably at least one drive is providedwhich is in particular configured as an electric motor or a hydraulicmotor.

To transfer vibrations in particular into the filling space of the screwseparator, at least one vibrating device may be provided. By means ofthe vibrating device vibrations are introduced into the feeder region,carrying over at least as far as the inlet region of the strainerbasket. The vibrating device is preferably mounted external of thefeeder region, transferring the vibrations of the vibrating device viasupporting ribs or similar means to a vibrator located in the liquid. Amembrane may ensure sealing from the interior. All the vibratingelements may be supported by springs or rubber buffers or the like,moving correspondingly at least in the vertical and/or horizontaldirection.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and possibilities of application of the presentinvention can be taken from the exemplary embodiment which will bediscussed below with reference to the accompanying figures.

These show in:

FIG. 1 a perspective view of an inventive screw separator in a closedposition;

FIG. 2 the screw separator from FIG. 1 with the ejection controller inan open position;

FIG. 3 the screw separator according to FIG. 1 with the front coverswung open;

FIG. 4 the screw separator according to FIG. 1 with the front cover wideopen;

FIG. 5 the screw separator according to FIG. 1 with some of thecomponents removed in an exploded view;

FIG. 6 a front view of the filter housing of the screw separatoraccording to FIG. 1 and a schematic cross-section;

FIG. 7 a schematic longitudinal cross-section of another screwseparator; and

FIG. 8 a cross-section of the screw separator according to FIG. 1.

DETAILED DESCRIPTION

The screw separator 1 illustrated in FIG. 1 in a slightly perspectiveview in a closed state comprises a housing 2. The housing 2 is providedwith a feed pipe 3 and with a discharge pipe 4 mounted in the lowerregion.

In the front region one can recognize the outlet 5 at the mouthpiece ofthe screw separator 1. The ejection controller 13 at the outlet 5comprises a flap cover mechanism 14 configured as a spring flap covermechanism comprising three cover sections 17 each being biased in theclosed position 15 as illustrated in FIG. 1 by way of springs 45 such asdisk springs or coil springs.

Unlike the illustrated embodiment the flap cover mechanism 14 mayconsist of four or five cover sections 17 each of which is separatelybiased in the closed position 15 by way of dedicated springs 45.

An inspection hole 23 provided with a cover that is for exampleconfigured as an inspection glass 25 and attached to the housing via aquick release 24 allows ready access to the interior of the screwseparator 1. With the inspection hole 23 closed by an inspection glass25, such inspection glass also permits inspecting the interior of thescrew separator 1 during operation. In this way one can for exampledetermine whether the filter screen of the strainer basket has cloggedup with residue or the like.

In operation a suspension is filled into the feed pipe 3 to be separatedby the screw separator 1 into liquid and solid constituents.

In operation a slug 35 will form (see FIG. 7) which is continuouslymoved towards the outlet 5 while new solid particles from the suppliedsuspension are continuously deposited at the rear end of the slug 35thus forming a new slug.

In FIG. 2 the ejection controller 13 with the flap cover mechanism 14 isillustrated in an open position 16 in which for example the pressurefrom the slug 35 (not illustrated here) opens the cover sections 17 ofthe flap cover mechanism 14 against the spring force of the springs 45such that the front part of the slug 35 is pushed out of the outlet.

In FIG. 3 the screw separator 1 is illustrated with the housing 2partially opened and in FIG. 4, fully opened.

The housing 2 comprises the filter housing 30 and the press housing 40which follows the filter housing 30 in the axial direction. It isclearly obvious that the two housing parts namely, the filter housing 30and the press housing 40 which serves as the front cover 32, areinterconnected via a hinge 37 which hinge 37 or swing mechanismcomprises two or presently three pivoting axes parallel to one anothersuch that the front cover 32 can be swung forwardly and then away to theside. The hinge 37 allows limited axial movement.

In the open position according to the FIGS. 3 and 4 the screw 7 isvisible in the filter housing 30, being provided with screw vanes 8 intwo screw flights 18 and 19 to thus provide a double-pitch screw 7.

In the axial direction the screw vanes 8 terminate in a separate ring orwearing ring 9 which is presently mounted at the front end of the filterhousing 30 to be freely accessible. This enables ease of replacement forthe wearing ring 9. Viewed from the feeder 3 towards the outlet 5, thestrainer basket 6 lies in front of the wearing ring 9. The ring orwearing ring 9 may consist of plastic and/or fiber-reinforced materials,at least in part of a metal or a metal alloy, or else of wood and inparticular hardwood.

In operation at least part of the liquid portion of the suspensionemerges outwardly passing through the strainer basket that is configuredas a filter screen and inside the filter housing 30 is diverted to thedischarge 4.

The press housing 40 is fastened to the filter housing 30 by means of aquick release 33 or else several quick releases 33. For closing thehousing 2 the front cover 32 is first swung towards the filter housing30. In closing, the front tip of the pipe 29 or the pipe-like structure36 enters the interior of the worm shaft 31 of the screw 7, thus guidingthe worm shaft during operation.

The slug 35 forming in the filter housing 30 or slug 35 already havingformed therein is presently hollow cylindrical in shape. The pipe 29following the axial end of the worm shaft 31 stabilizes the interior ofthe slug 35. The fact that the outer diameter of the pipe 29 is matchedto the outer diameter of the worm shaft 31 ensures ease of transition ofthe slug onto the pipe 29 in the press housing 40. The pipe 29 maylikewise be configured slightly conically, tapering or widening in theaxial direction.

In the press housing 40 the press basket 10 is provided through thefilter surface of which the remaining squeezed-out liquid can emergeradially outwardly into the housing 2 before the slug 35 emergesoutwardly through the front mouthpiece or the outlet 5. The separatedsolids can then be put to suitable use.

FIG. 5 shows a schematic exploded view of the screw separator 1 in anopen position. One can clearly recognize the wearing ring 9 mountedaxially in front of the filter housing 30. In front of the press housing40 the press basket 10 and the pipe 29 or the pipe-like structure 36 isillustrated which serves as an axial extension of the worm shaft 31.

FIG. 6 shows a front view of the filter housing 30 allowing a look intothe interior of the screw separator 1. The suspension supplied throughthe feed pipe 3 arrives in the feeder region 38 (see FIG. 8) and bymeans of the screw 7 is conveyed forwardly in the direction of theoutlet 5.

The worm shaft 7 carries the screw vanes 8 and is guided tight in thestrainer basket 6. The strainer basket 6 is configured as a filterscreen, comprising rods arranged over the periphery in parallel in thelongitudinal direction and spaced apart by gaps in the peripheraldirection between about 1 and 2 mm. The exact gap size depends on theintended application and may be smaller or larger in relation to thematerials to be separated.

Over the outer periphery of the strainer basket 6 three rods 43 aredistributed symmetrically, being secured to the strainer basket 6 andproviding a radially floating support of the strainer basket 6 andpreventing the strainer basket 6 from rotating along with the screw 7.To this end a total of four rods 44 are presently provided in thehousing 2 serving as retaining means to prevent the strainer basket 6from rotating along. The arrangement principle of the rods 43 and 44 isshown in the schematic cross-section on the right in FIG. 6. One rod 43of the strainer basket is provided on both sides with rails or rods 44in the filter housing while only one rod 44 each is provided in thehousing for the other rods 43. Since the screw 7 will always only rotatein one direction it is sufficient to provide two rods in the filterhousing 2 for one rod 43 only. The strainer basket 6 is radially movablein the housing 2 by about 2 mm such that the strainer basket can adjustto occurring stresses.

One or more inspection holes 23 may be provided in different places withtransparent or non-transparent covers.

The feed pipe 3 or the feeder region 38 may be provided with a vibratingdevice 34 to intentionally introduce vibrations into the suspension ormatter contained to achieve homogeneity of distribution and highefficiency of the screw separator 1. FIG. 7 shows a simplistic and inparticular not true to scale cross-sectional view of a screw separator1. The illustration in FIG. 7 shows in a highly magnified scale that theinner diameter 28 of the press basket is larger than the inner diameter42 of the wearing ring 9 which in turn is larger than the inner diameter20 of the strainer basket 6. The fact that each subsequent component issomewhat larger in its inner diameter than the preceding componentallows to ensure that the slug 35 passes unobstructed from one componentto the next.

This construction in particular allows to considerably increase themanufacturing tolerances for the press basket 10 so as to largelysimplify manufacturing and reduce costs. The dimensions of the wearingring 9 and of the press basket 10 ensure that their inner diameters arelarger than is the inner diameter 20 of the strainer basket 6.

The pipe-like structure 36 or the pipe 29 inside the slug 35 stabilizethe slug, preventing it from collapsing. The pipe 29 is in particularconfigured stationary so as to quite considerably reduce wear on thepipe 29. In conventional screw separators in which the worm shaft 31extends to the exterior through the mouthpiece beyond the press basket,the pipe continuously rotates with the slug 35 that virtually does notrotate along.

In a conventional screw separator 1 the relative speed between theoutside of the worm shaft 31 and the slug 35, given a worm shaftdiameter of approximately 10 cm and a rotational speed of approximately30 revolutions/minute, is roughly estimated 15 cm/second. In thisexample the advance rate of the slug is approximately 1 cm/second. Thismeans that the relative speed between the slug 35 and the worm shaft 31is a combination of the advance rate of 1 cm/second and the relativerotational speed of approximately 5 cm/second. For the screw separator 1the relative speed between the slug 35 and the pipe 29 in the pressbasket 10 is approximately 1 cm/second thus corresponding to the advancerate of the slug 35 since the pipe is mounted stationary. In the regionof the press basket 10 the stresses are highest since this is where thehighest pressures occur. By means of this measure, wear can be reducedquite considerably.

The additional dotted line denotes a cone section 41 of anotherconfiguration of a screw 7 where the screw vanes 8 are radially taperingover an axial section 39. Here the largest radial diameter lies in theregion of the ring 9. The axial section 39 over which the screw vanesradially taper may extend as far as and into the press basket 10. Thenthe worm shaft 31 extends as far as the edges of the screw vanes 8. Asuitable pipe 29 may be axially mounted at the rear of the worm shaft31. In this configuration of the screw vanes 8, also shown in a dottedline, the region of maximum stress again lies within the wearing ring 9.This configuration allows for the screw vanes to formally extend as faras into the press basket 10 while the stresses within the press basket10 are concurrently reduced so as to increase durability. A steppedtapering is in particular conceivable.

The radial gap 22 between the outer diameter 21 of the screw vanes 8 andthe inner diameter 20 of the strainer basket is intentionally small, forexample 0.5 mm, while the outer diameter of the screw vanes may be 20cm, 25 cm, or even 30 cm. This very narrow gap prevents water or thesuspension from spurting forwardly which would interfere with slugformation. Furthermore the screw vanes 8 continuously free the strainerbasket 6 interior from residues, thus preventing clogging up.

FIG. 8 shows a longitudinal cross-section of the screw separator 1. Thesuspension to be separated is fed to the feeder region 38 from where itis conveyed towards the strainer basket 6 by means of the screw vanes 8.

In the axially and radially floating strainer basket 6 the suspensioncharge is continuously compacted to thus form a slug 35 from the solidscontained while the aqueous constituents run outwardly through thestrainer basket 6 at least in part, draining off through the discharge4. The screw vanes 8 terminate in the axial direction in a wearing ring9 that is provided as a replaceable part.

The screw 7 is rotatably supported on the feeder side 11 and at its freeend 12 it is guided by the pipe-like structure 36. It is as wellconceivable to support the screw 7 at both ends.

The housing 2 consists of the filter housing 30 and the press housing 40which is provided as a front cover 32 that can be swung away.

The front cover 32 is provided with a flap cover mechanism 14, presentlyhaving three cover sections 17 that are biased in the closed positionvia springs 45.

A pipe-like structure 36 is also retained in the front cover 32configured as a hollow or else a solid pipe 29 which when closed axiallyfollows the end of the worm shaft 31 which it guides.

On the whole the invention provides a screw separator which ensures highfunctional reliability, high durability, and reliable operation whilealso offering ease of maintenance.

Due to a separate ring 9 being provided between the strainer basket 6which serves as a dewatering screen and the press basket 10 in which theeffective portion of the screw vanes 8 terminates, the strainer basket 6is subjected to reduced wear so as to achieve increased durability. Thisis again supported by the fact that the strainer basket 6 is received inthe housing 2 to be radially floating while the press basket 10 isaxially and radially fixed in the housing 2.

Another considerable advantage is the separate construction of the pipe29 which axially follows the worm shaft 31 that terminates inside thehousing 2. For one the pipe 29 ensures that the slug 35 retainsstability inside the press basket 10 and for another the pipe 29received in particular stationary considerably reduces wear on the wormshaft 31.

On the whole a screw separator 1 offering flexible applications isprovided which achieves high durability at low operational costs.

While a particular embodiment of the present screw separator has beendescribed herein, it will be appreciated by those skilled in the artthat changes and modifications may be made thereto without departingfrom the invention in its broader aspects and as set forth in thefollowing claims.

The invention claimed is:
 1. A screw separator for separating solids outof suspensions, comprising: at least one housing and at least one feedpipe for a suspension, said at least one housing including a pluralityof rods; at least one discharge pipe for liquids; at least one outletfor at least partially dewatered solids; at least one strainer basketprovided in the at least one housing, said at least one strainer basketincluding at least one rod extending from said at least one strainerbasket; a screw rotatably mounted in the at least one housing; and atleast one press basket mounted downstream of the at least one strainerbasket in the at least one housing, wherein the at least one strainerbasket is disconnected from and radially floating in the at least onehousing, said at least one rod of said at least one strainer basketbeing positioned between and spaced from two of said plurality of rodsof said at least one housing such that said at least one rod of said atleast one strainer basket engages said two of said plurality of rods ofsaid at least one housing to inhibit movement of said at least onestrainer basket in either rotational direction relative to said at leastone housing, and wherein the at least one press basket is radially fixedto the at least one housing.
 2. The screw separator according to claim1, wherein a press housing is configured as a front cover which can beswung or pivoted away from the at least one housing.
 3. The screwseparator according to claim 1, wherein a replaceable ring is mountedbetween the at least one strainer basket and the at least one pressbasket.
 4. The screw separator according to claim 3, wherein thereplaceable ring is a wearing ring that is configured to be tight in aradial direction.
 5. The screw separator according to claim 4, whereinthe at least one press basket and the wearing ring are mounted in afront cover.
 6. The screw separator according to claim 2, wherein thefront cover is provided with the at least one outlet.
 7. The screwseparator according to claim 1, wherein at least one ejection controlleris provided at the at least one outlet.
 8. The screw separator accordingto claim 1, wherein the at least one outlet includes a flap covermechanism comprising at least three flap cover sections which aredistributed over a circumference of the at least one outlet.
 9. Thescrew separator according to claim 2, wherein a pipe is mounted in thepress housing axially following a worm shaft of the screw and extendingoutwardly through the at least one outlet.
 10. The screw separatoraccording to claim 9, wherein at least part of the pipe is receivedrotatably.
 11. The screw separator according to claim 9, wherein atleast part of the pipe is received stationary.
 12. The screw separatoraccording to claim 1, wherein an inner diameter of the at least onepress basket is larger than an inner diameter of the at least onestrainer basket.
 13. The screw separator according to claim 1, furthercomprising at least one vibrating device configured to generatevibrations that are introduced into a feeder region on the at least onehousing such that the vibrations carry into an inlet region of the atleast one strainer basket.
 14. The screw separator according to claim13, wherein the at least one vibrating device is arranged externally ofthe feeder region, wherein the vibrations are transferable viasupporting ribs to a vibrator located in a liquid in the at least onehousing; and wherein a membrane ensures that an interior is sealed andall vibrating elements are supported by one of springs or rubber buffersallowing movement at least in a vertical direction.